Heat-sealed plastic bags are well known in the packaging industry. Such bags have been used to seal foods, medical supplies and equipment, pharmaceuticals, health care products and the like. In many cases, the bags are used to reduce product contamination and deterioration by preventing entry of bacteria or other pathogens. The bags can also serve the function of evidencing product tampering. In the medical supply and equipment industries, the bags are frequently gas-permeable.
Designs (i.e., shape, length and diameter) of tortuous or labyrinthine passages effective in substantially preventing bacterial and viral access are well known in the art. For instance, one such design is a tortuous passage integrated into a wall or side panel of a sterile package or container, while utilizing a separate means for finally sealing the package and thus protecting its contents. Another prior art design includes a tortuous passage incorporated into a seal, but requires an additional material as noted above, such as Tyvek.TM. paper, to prevent entry of contaminants. The Tyvek.TM. or other surgical latex coated paper acts as a three-dimensional barrier used in conjunction with weld-type seals. In addition, the prior art designs generally utilize labyrinthine seals formed in three dimensions, such as by carefully aligning, overlapping and pressing together a pair of discs, a time consuming and expensive process, which necessarily would raise the price of the final product.
One prior art heat-sealed, gas-permeable bag used in packaging plastic medical products consists of a single rectangular plastic piece that is folded at about the middle of its length, and heat sealed along the three open edges to form an approximately square sealed bag. To provide gas permeability, the rectangular plastic piece, prior to the folding and sealing steps, is perforated at several places in a band spanning the width of the bag. To prevent entry of bacteria, a strip of Tyvek.TM. paper is heat sealed over an area that encompasses the perforations. At least two heat-sealing steps are performed to secure the barrier paper to the bag. Tyvek.TM. and other surgical latex coated papers in this application act as a three-dimensional barrier that operates in conjunction with weld seals.
The bag is required to be gas-permeable because sterilization of the medical product sealed in the bag can result in the accumulation of toxic or malodorous gases in the bag. If sterilization is via gamma irradiation, the released malodorous gases should be vented. If sterilization is with ethylene oxide, the gas must first diffuse into the bag to sterilize the product, and must later diffuse out of the bag to reduce potentially toxic gas to acceptable levels. Some manufacturers sterilize their medical products in sealed bags with slits or pinholes to provide gas exchange. While such bags can be less expensive to manufacture, the likelihood of contamination with pathogens is much greater with products packaged in this manner.
In the medical supply and other industries, there is a continuing need to reduce packaging costs without compromising product sterility. The subject invention can reduce packaging costs while maintaining permeability of a bag or other package to gases and maintaining product sterility.